Skin Cancer Basics

Skin cancer is an abnormal growth of skin cells that forms when tissue grows at an uncontrollable and unpredictable rate. It is the most common and rapidly increasing form of cancer in the United States. Overexposure to sunlight, including tanning, is considered to be the leading cause of skin cancer. Fair-skinned people who sunburn easily are at a particularly high risk for developing skin cancer. If detected early, skin cancer can be treated successfully. The most common types of skin cancer include basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.

Causes of Skin Cancer

The leading cause of skin cancer is overexposure to ultraviolet (UV) light, whether through sunlight or tanning beds. UV light damages the DNA with repeated exposure. The effects of sun damage are cumulative over many years and typically result in most skin cancers appearing in later adulthood. Heredity also plays a part. Family history is a strong indicator of risk in certain ethnic groups. Fair-skinned people who sunburn easily are at a particularly high risk for developing skin cancer. Other causes include repeated medical and industrial X-ray exposure, scarring from severe diseases or burns and occupational exposure to certain chemical compounds. Immunosuppressed patients, such as organ transplant recipients or patients with chronic lymphocytic leukemia (CLL) are at greatly increased risk as well, because their immune systems are not as capable of warding off cancerous cells.

Types of Skin Cancer

The 3 most common types of skin cancer account for approximately 99% of all skin cancers. They are listed below.

1. Basal Cell Carcinoma (BCC)

Basal cell carcinoma is the most common type of skin cancer, accounting for about 80% of all diagnosed skin cancers. It arises from the bottom or base of the uppermost skin layer (epidermis). Most do not spread beyond the skin to other parts of the body. They typically grow slowly on the skin but should be removed because of the extensive local damage they can cause in surrounding tissue. A BCC can have many appearances. Typically it appears as a small pearly or pink skin-colored bump. It may also appear as a scar-like growth or scaly area. Untreated, the cancer often will bleed, crust over, heal, and repeat the cycle.

2. Squamous Cell Carcinoma (SCC)

Squamous cell carcinoma is the second most common type of skin cancer. It develops from cells above the bottom of the epidermis known as squamous cells. This is a potentially more dangerous type of cancer than BCC because of its ability to sometimes “break away” (metastasize) from the skin and spread to local lymph nodes or less commonly to distant areas of the body. This occurs more often with large, aggressive squamous cell carcinomas or rapidly-growing tumors on the ears, scalp, lips or genitalia. An increased risk of spread is also seen in patients that are immunosuppressed, such as organ transplant patients, or those with chronic lymphocytic leukemia (CLL), or in tumors that have recurred after previous treatment. SCC may appear as a persistent rough scaly area or a hard red bump. It also commonly arises on areas that are chronically exposed to the sun, such as the face, scalp, neck, upper back, and arms.

3. Malignant Melanoma (MM)

The third most common type of skin cancer also has the potential to be the most dangerous, accounting for 75% of all skin cancer related deaths. Melanoma develops from melanocytes, the skin cells that produce the pigment called melanin, which give the skin, hair and eyes their color. Its appearance can vary but the cancer classically has mixed shades of brown and black with asymmetry and irregular borders. It can develop in a mole or appear as a new mole. Less commonly it can also be red or white. Melanoma has a strong tendency to metastasize (spread) to distant organs and can thus be life threatening. Fortunately, early detection and surgical removal can result in a high cure rate. Once melanoma has spread, the cure rate reduces significantly.

Sun exposure, especially sunburn, is the most important preventable cause of melanoma. Individuals with light skin and light eyes have the most risk. Heredity also plays a part. A person with a relative or close family member that has had melanoma has an increased chance of developing melanoma. Atypical moles (dysplastic nevi), which may run in families, and having a large number of moles, can serve as markers for people at increased risk for developing melanoma.